1. Field of the Invention
The present disclosure relates to a reading apparatus capable of reading an image of a document.
2. Description of the Related Art
A reading apparatus that reads an image of a document while allowing the document and an image sensor to make a relative movement is known. One type is a flatbed type scanner (abbreviated as an FBS in the specification) that performs scanning and reading while moving an image sensor (a line sensor) relative to the document fixed on a document positioning plate. Another type is a sheet-through type scanner that performs scanning and reading while moving a document relative to a fixed image sensor (a line sensor). A unit that separates and moves documents one by one is referred to as an auto document feeder (abbreviated as an ADF in the specification).
Japanese Patent No. 2627044 discusses a reading apparatus having a combination of these types. The apparatus discussed in Japanese Patent No. 2627044 uses a direct current (DC) motor as a driving source for a sheet movement by an ADF, and has a code wheel (a spinning disk) of an encoder for detecting a motor rotation state attached to a rotational shaft of the motor.
In the ADF of the apparatus discussed in Japanese Patent No. 2627044, a transmission mechanism including gears, a drive shaft, a pulley, an endless belt, and a clutch transmits an output from a DC motor to a roller group that conveys documents. The DC motor is arranged apart at the back side of the apparatus across the transmission mechanism. Consequently, both sides of the DC motor form a large dead space, and the area of the apparatus in a depth direction is uselessly large
Further, in the ADF of the apparatus discussed in Japanese Patent No. 2627044, a worm gear and a code wheel of the encoder are attached adjacent to each other to a rotational shaft of the DC motor. Since the rotational shaft needs to be made longer, positional deviation of the code wheel is amplified even when the rotational shaft has a slight inclination or bend. Thus, the positional deviation leads to deterioration of detection accuracy of the encoder. In addition, grease used for lubrication of the worm gear is likely to adhere to the adjacent code wheel or an encoder sensor, so that the soiling leads to deterioration of detection accuracy of the encoder.